Why does the NeutronHP model in Geant4 v11.2.2 give warnings about missing files for Argon isotopes, when this issue did not occur in Geant4 v11.2.1 and v11.0.3, and how can it be resolved?

Physics Processes, Models and Cross Sections
1

When I was using Geant4 V11.2.2, the following information appeared when running the program. However, such a problem did not occur in Geant4 v11.2.1 and v11.0.3. I suspect that it was caused by the code changes of the newly added model in v11.2.2. But how to solve it?

NeutronHP: /Capture file for Z = 18, A = 36 is not found and NeutronHP will use /home/esword/.local/software/geant4/11.2.2/share/Geant4/data/G4NDL4.7.1/Capture/CrossSection/18_37_Argon
NeutronHP: /Elastic file for Z = 18, A = 36 is not found and NeutronHP will use /home/esword/.local/software/geant4/11.2.2/share/Geant4/data/G4NDL4.7.1/Elastic/CrossSection/18_37_Argon
NeutronHP: /Inelastic file for Z = 18, A = 36 is not found and NeutronHP will use /home/esword/.local/software/geant4/11.2.2/share/Geant4/data/G4NDL4.7.1/Inelastic/CrossSection/18_37_Argon
NeutronHP: /Capture file for Z = 18, A = 38 is not found and NeutronHP will use /home/esword/.local/software/geant4/11.2.2/share/Geant4/data/G4NDL4.7.1/Capture/CrossSection/18_39_Argon
NeutronHP: /Elastic file for Z = 18, A = 38 is not found and NeutronHP will use /home/esword/.local/software/geant4/11.2.2/share/Geant4/data/G4NDL4.7.1/Elastic/CrossSection/18_39_Argon
NeutronHP: /Inelastic file for Z = 18, A = 38 is not found and NeutronHP will use /home/esword/.local/software/geant4/11.2.2/share/Geant4/data/G4NDL4.7.1/Inelastic/CrossSection/18_39_Argon

_Geant4 Version: 11.2.2
_Operating System: AlmaLinux 9.4
_Compiler/Version: 11.4.1
_CMake Version: 3.26.5

2

I don’t think there is anything to solve. In the 11.2.2 release notes it says:

  • models/particle_hp:
    o G4CrossSectionHP: …
    Fixed elastic and capture cross-sections in Argon, by using only the main
    isotope Z=18, A=40 (there was up to 50% overestimation of cross-sections
    due to wrong data for rare isotopes of argon).

and

Data
----
+ G4NDL-4.7.1:
o Removed all files for Argon-36 and Argon-38 as significantly different
from those of ENDF/B-VIII.0.

So this is intended behaviour by the developers.

3

Will this modification have a significant impact on my experimental simulation?
I am a beginner of Geant4 and don’t know much about these.

4

Of course, if you have no argon in your simulation, then it makes no difference at all. If you have air in your geometry, elemental argon comprises only 0.934% of the gases in air and Ar-40 is 99.6 % of the elemental argon (Ar-36 is 0.334%, Ar-38 is 0.063%). So it will make a very small, likely negligible, difference.

If you have a pure natural or single isotope argon target, it will make a difference but I am unsure how much. The release notes suggest it will improve estimates, but the developers might want to jump in with a more quantitative answer.

5

Oh oh, mine. Thank you for your answer. I understand!

6

Hi @Esword

Thanks for reporting!

I think @John_McFee gave already the answer, here it is the plots with the cross sections for argon. I think the original error happened in the data evaluation, and then propagated to Geant4.

I will open a bugzilla ticket regarding the error message.

Best,
Alvaro

7

Can you try installing the previous version G4PARTICLEXS 4.0?